Audi P0430

Bank 2 cat efficiency on Audi V6/V8 — typically upstream misfire damage, lazy rear O2 or coolant ingestion on 3.0T/4.2 FSI.

Audi P0430 — Bank 2 cat efficiency on Audi V6/V8 — typically upstream misfire damage, lazy rear O2 or coolant ingestion on 3.0T/4.2 FSI. Typical UK independent garage cost: £260–£2800.

What actually causes P0430 on a Audi

Audi V engines run two cats and the bank-2 (passenger side, RHD) is buried — labour cost dominates. P0430 on 3.0T is often a cracked passenger-side exhaust manifold or a lazy O2 sensor; on 4.2 FSI it's carbon and oil-burn from worn valve stem seals. Always rule out the failing plastic thermostat housing on 3.0T — coolant in the cat is death.

Audi engines that log P0430

• 3.0T supercharged (S4/S5/Q5)
• 2.7T BiTurbo (A6/A4/allroad)
• 4.2 FSI V8 (RS4/RS5/S5)
• 3.0 TDI BiTDI (A7/Q7)

How we diagnose P0430 on a Audi

1. Identify Bank 2 correctly on Audi V-engines (cyl 4-6, passenger side RHD)
2. Inspect exhaust manifold for hairline cracks — common on 3.0T
3. Test rear O2 sensor — slow switching = lazy cat
4. Check coolant level history for failed thermostat housing — coolant ingestion kills cats
5. Compression test if cylinder misfires logged alongside

The common misdiagnosis to avoid

Indie quotes for both cats when only one is faulty — insist on per-bank diagnosis. Aftermarket cats on 4.2 FSI fail emission re-tests; OEM only.

Audi P0430 repair cost in the UK

Expect £260–£2800 including parts and labour at an independent garage. Main-dealer quotes on Audi are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

Audi V-engine P0430 always check the thermostat housing first on 3.0T — a £180 housing job avoids a £2k cat replacement six months later.

Codes usually seen alongside P0430 on Audi

• P0420
• P2096
• P0011
• P0014

Symptoms drivers report with P0430

• MIL comes on after a motorway run then stays lit — no drivability change
• Slight sulphur/rotten-egg smell on hard acceleration
• MPG drop of 1–3 mpg you wouldn't notice unless you track it
• Fails emissions/lambda snapshot at MOT despite passing tailpipe CO
• Bank 2 short-term fuel trim slightly richer than bank 1 at cruise

Repairs that clear P0430

• Same diagnostic as P0420 but bank 2 side
• Replace bank 2 rear lambda first as trial
• Confirm with lambda graphing before cat replacement

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0430 guide.

Reading P0430 on a Audi properly

A generic reader will show P0430 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Audi has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0430 without fixing it

Erasing the code resets the Audi's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0430 is showing on your Audi, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.